Avoiding data collisions is one of the roles of various media access (MAC) protocols. For example, carrier sense and exchange of request-to-send (RTS) and clear-to-send (CTS) packets have been used to prevent concurrent communication in wireless networks. Yet these approaches can prevent all concurrent communication, even exchanges that might not result in loss; they reduce end-to-end throughput in a multi-hop network; moreover, control traffic imposes control overhead on networks with small data payloads.